SrTiO₃シードバッファー層の導入によるPb(Zr, Ti)O₃ (PZT) 薄膜の結晶成長

抄録

It has been reported that preparation of crystallized single phase Pb(Zr, Ti)O₃ (PZT) (perovskite structure) thin film on Pt/Ti/SiO₂/Si and Pt/Ir/SiO₂/Si substrates by pulsed laser deposition (PLD) method is difficult, and a pyrochlore-type compound forms instead of PZT; however, the reason for this has not been clarified. In this work, it was found that such instability of PZT is caused by the evaporation of Pb during the deposition. It was also found that the evaporation of Pb can be suppressed by introducing a very thin SrTiO₃ (ST) seed buffer layer to the surface of Pt/Ti/SiO₂/Si and Pt/Ir/SiO₂/Si substrates. Moreover, it was found that the peak intensity of PZT changes with the thickness of the ST seed buffer layer, and maximum peak intensity was obtained when the thickness of ST was 2nm. When the thickness of the ST seed buffer layer was less than 1nm, considerable coexistence of the pyrochlore-type compound was detected, therefore the remanent polarization (P_r) was lowered. Single-phase PZT thin films can be obtained if the thickness of ST is over 2nm, however, if the thickness of ST is over 4nm, the P_r value is decreased.